The invention relates to the field of electronic components parts, in particular, low profile inductors that are intended to be surface mounted.
The explosion in computer design, cellular telephones, etc., especially the interest in making such devices truly pocket-sized yet maintaining or even increasing overall performance has resulted in a quest for smaller and smaller component parts. The need for a surface mounted inductor having extremely low profile when mounted has been especially acute. Applications such as notebook, PC cards, wireless communication devices, handheld PDAs and the new line of Windows Powered (Windows CE-based) Pocket PCs are limited in size reduction to size of the largest parts. This problem has added further impetus to continue seeking methods to manufacture still smaller parts. The need for extremely low profile inductors surface mountable on a circuit board is especially acute. Of course, this need for a very small inductor must be weighed against the cost of manufacturing such a part. The goal, of course, is to achieve both . . . an extremely small profile and a reduced cost of manufacture.
One solution for this type of inductor is manufactured by Coilcraft of Cary, Ill. identified as their LPT3305 Series. This device uses toroid construction which minimizes electromagnetic interference and utilizes a ceramic cover so that the device can be installed using xe2x80x9cpick and placexe2x80x9d assembly. The profile of this device is approximately 1.8 mm in thickness or greater due to prefabricated cover. The device has an xe2x80x9cup/downxe2x80x9d orientation and must be mounted right side up. The ceramic cover encloses primarily only the top of the wound toroid. The cover and the pair of connection terminals are made separately and must accomplished in multiple steps. Also, the cover and the pair of connection terminals are also made separately, thereby adding to the cost of manufacture and reducing reliability due to the interconnect.
Another representative of this genre of low profile inductor is made by Coiltronics sold under the trademark THIN-PACs. As with Coilcraft product, the prefabricated cover essentially surrounds only the top of the toroid leaving most of the bottom open. The thickness of this device is approximately 1.8 mm in thickness or greater, again due to the prefabricated cover. Also, as with the Coilcraft product, adhesive must be used to hold the wound toroid in place when the prefabricated cover is applied.
A low profile surface mounted inductor of comparable electrical performance having a thickness of no more than 1.5 mm and the same outline dimensions otherwise, that can be made in a single step, and has either an xe2x80x9cup or downxe2x80x9d mounting orientation is not found in the prior art.
The invention is a surface mountable low profile inductor. A toroidal core is provided. At least one predetermined length of wire having a predetermined diameter is also provided. The wire is wound around the toroidal core in a plurality of loops to provide a wound toroid. A pair of lead ends corresponding to each length of said wire extends from the wound toroid. An integrated molded housing features a cover and at least two wrap posts. Each of the wrap posts has a wire end. The cover at least partially encapsulates the wound toroid. In the preferred embodiment, each wrap post at least partially encapsulates the corresponding lead end of said wire so that a wrap portion of the lead end extends through its wrap post. However, lead ends may not exit the wrap post but instead may exit the periphery of the cover. Finally, the inductor is completed by providing a plurality of surface mount pads with each surface mount pad provided by the wrap portion being wrapped around its corresponding wrap post.
Therefore, it is an aspect of the invention to provide a surface mounted low profile inductor that can be insert-molded in a single step.
Another aspect of the invention to provide an aspect of the invention to provide a surface mounted low profile inductor that has a profile of less than or equal to 1.5 mm in thickness without compromising other dimensions or electrical performance.
Still another aspect of the invention is to provide a surface mounted low profile inductor that can be used with standard xe2x80x9cpick and placexe2x80x9d positioning techniques well known in the art.
Another aspect of the invention to provide an aspect of the invention to provide a surface mounted low profile inductor that can also be mounted upside down as well as right side up.
Finally, it is an aspect of the invention to provide a surface mounted low profile inductor that be inexpensively produced yet meets today""s IC performance and size requirements.